1. Field of the Invention
The present invention relates to an antenna for use in various radio communications apparatuses.
2. Description of the Related Art
A small-sized antenna for use in various radio communications apparatuses such as a mobile phone is known, as shown in FIG. 7. This antenna includes a basebody 1 made of a dielectric or a magnetic material, a radiation conductor 2, and a power supplier 3 formed in the basebody 1 (for example, Japanese Patent Laid-Open Publication No. H10-247808).
However, in the case where the basebody 1 is made of mono dielectric material, mono magnetic material, or a mixture of mono dielectric material and mono magnetic material, the basebody 1 has a constant magnetism distribution or a constant permittivity distribution. For example, if the basebody is made of a mono dielectric material, the capacitive coupling of the radiation conductor 2 with a ground plate (not shown) is larger, whereby it makes it easier to form a loading capacity for wavelength compression at an open end 2a, but the impedance of the radiation conductor 2 itself is lower. As a result, it is necessary to set large a physical length of the radiation conductor 2 in order to secure its specified electrical length. Thus, it has been difficult to miniaturize the antenna.